ASN Wikibase Occurrence # 147490
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| Date: | Tuesday 7 August 2012 |
| Time: | 08:45 |
| Type: |  Bell 214ST |
| Owner/operator: | Bell Helicopter Textron Inc |
| Registration: | N409SB |
| MSN: | 28199 |
| Year of manufacture: | 1990 |
| Engine model: | General Electric CT7-2A |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Ellis County, 10 mi N of Avalon, TX -
 United States of America
|
| Phase: | En route |
| Nature: | Test |
| Departure airport: | Arlington Muni, TX (KGKY) |
| Arlington Muni, TX (KGKY) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter was on its third test flight when the tail rotor 90-degree gearbox broke in two and separated from the helicopter. The crew conducted an autorotation to a field, and the helicopter came to rest on its side. Examination of the helicopter and components revealed that one of the tail rotor’s two counterweight bellcranks and associated hardware were missing. Impact marks consistent with a counterweight bellcrank were found at the base of its associated tail rotor blade and on the aft right side of the helicopter. The remaining counterweight bellcrank was in place; however, the cotter pin for the castellated nut was missing. A review of the aircraft maintenance records revealed that the tail rotor assembly had been removed and reinstalled after the installation of test instrumentation. The maintenance records lacked specific details on whether the unit and its components were previously handled as a subassembly or as individual components when the tail rotor assembly was initially removed. Because the records did not indicate whether the unit should be handled as individual parts, the tail rotor was reinstalled as a complete subassembly, meaning that individual components, such as the nut and cotter pin, were not individually inspected before or after reinstallation on the helicopter. Reinstalling the tail rotor assembly in this manner led to the counterweight bellcrank retaining nut not being properly torqued and secured with a cotter pin.
Probable Cause: Maintenance personnel’s failure to properly torque the retaining nut and install the cotter pin that secured the helicopter’s tail rotor counterweight bellcrank. Contributing to the accident was the lack of detailed maintenance records that documented previous maintenance actions.
Accident investigation:
 |
|
Sources:
NTSB
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 07-Aug-2012 12:30 | gerard57 | Added |
| 07-Aug-2012 15:54 | Geno | Updated [Time, Aircraft type, Registration, Cn, Operator, Location, Nature, Departure airport, Destination airport, Source] |
| 08-Aug-2012 09:34 | Geno | Updated [Registration, Cn, Source, Narrative] |
| 09-Aug-2012 09:45 | Geno | Updated [Time, Phase, Source, Narrative] |
| 12-Aug-2012 12:08 | Anon. | Updated [Source, Narrative] |
| 20-Feb-2013 09:00 | TB | Updated [Time, Operator, Location, Source, Narrative] |
| 20-Feb-2013 09:10 | TB | Updated [Source] |
| 24-Feb-2013 08:50 | TB | Updated [Operator] |
| 15-Aug-2014 17:56 | Aerossurance | Updated [Phase, Source, Narrative] |
| 08-Jul-2016 08:48 | Aerossurance | Updated [Time, Source] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 28-Nov-2017 13:17 | ASN Update Bot | Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
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